The recent rapid advance in the network communication technologies including the Internet has realized the provision of so-called cloud services by which users can get various kinds of content via networks. Use of cloud computing services allows each user to use particular pieces of content even if the user does not have application programs for realizing these pieces of content.
In addition, the advance in recent computer technologies is remarkable. For example, in the past, such content costly in computation as game applications required the hardware dedicated to the execution, but a so-called game emulator that executes game applications by emulating the hardware in the software approach has become practical.